Various synthetic and natural water-soluble polymers have been developed which exhibit superior thickening and flocculating properties in aqueous solutions. These polymers are being used increasingly in a number of commercial applications such as in the clarification of aqueous systems, in paper making operations, in the treatment of sewage and industrial waste, in stabilizers for drilling muds, and in the secondary recovery of petroleum by water flooding.
Although these polymers are available commercially as powders or as finely divided solids, they are most frequently utilized as aqueous solutions. This requires the solid polymer material to be dissolved in water. This is a time consuming step as well as one which has serious drawbacks with respect to the actual dispersion of solids into the aqueous media.
Water-in-oil emulsions having finely divided water-soluble polymers dispersed therein are known in the art. The primary disadvantage of such emulsions is that attempted further treatment of such emulsions generally results in coagulation or agglomeration of the polymer whereby the polymer does not remain finely divided and dispersed in the emulsion.
Attempts to add surfactant to such emulsions to render the emulsions self inverting, whereby the polymer can be dispersed in aqueous solutions, have generally not been successful as a result of coagulation or agglomeration of the polymer. As a result, usually such emulsions are inverted into water by separately adding the surfactant and emulsion to the water, which necessitates separate shipping and handling of two products.
In U.S. Pat. Nos. 3,624,019 and 3,734,873, it is indicated that it is possible in some cases to prepare a self inverting water-in-oil emulsion having finely divided polymer and surfactant dispersed therein. However, there are limitations in that the addition of the surfactants may tend to interact with the emulsifier or emulsion and destroy it prior to use thereof.
Prior art references of interest relative to the present invention are those which are concerned with the production of stable water-in-oil emulsions of water-soluble polymers which are adapted for self inversion in aqueous solutions.
U.S. Pat. No. 4,052,353 describes a self water dissolving composition of a water-soluble polymer dispersed in oil which is comprised of (1) a water-in-oil dispersion of a water-soluble polymer, wherein the water content of the dispersion has been reduced by distillation to less than 40 weight percent; and (2) a water-soluble surfactant having an HLB number above 8.
Other prior art of interest relating to dispersions of water-soluble polymer in oil include U.S. Pat. Nos. 3,282,874; 3,691,124; 3,826,771; 3,849,361; 3,888,945; 4,021,399; 4,024,097; 4,029,622; 4,090,992; 4,125,508; 4,176,107; and 4,299,755.
There is continuing interest in the development of stable water-in-oil type dispersions of water-soluble polymers which are dispersible in aqueous solutions, and which preferably have a high solids content of water-soluble polymer.
Accordingly, it is an object of this invention to provide a stable water-in-oil dispersion of water-soluble polymer which is readily dispersible in aqueous media.
It is another object of this invention to provide a process for the production of a non-gelling water-in-oil dispersion of water-soluble polymer, which dispersion contains more than about 40 weight percent of water-soluble polymer.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.